Truck fault codes
What every diesel truck SPN/FMI and OBD code means, the most likely cause, and the test that confirms it. Free, no account.
Aftertreatment / DPF
- P2002DPF efficiency below threshold · The truck's control module (ECU) reports a fault on: DPF efficiency below threshold.
- SPN 3242DPF intake temperature · The truck's control module (ECU) reports a fault on: DPF intake temperature.
- SPN 3246DPF outlet temperature · The truck's control module (ECU) reports a fault on: DPF outlet temperature.
- SPN 3251 FMI 0Particulate filter · The particulate filter is plugged and the engine is losing power.
- SPN 3719DPF soot load · The truck's control module (ECU) reports a fault on: DPF soot load.
Air intake / Turbo
- P0299Turbo underboost · The turbo is not making the boost the engine asks for.
- SPN 102 FMI 18Boost pressure · Intake manifold pressure is low: the truck is down on power.
- SPN 105Intake manifold temperature · The truck's control module (ECU) reports a fault on: Intake manifold temperature.
- SPN 641Turbo actuator (VGT) · The truck's control module (ECU) reports a fault on: Turbo actuator (VGT).
Ambient
Auxiliary
Brakes / ABS
- SPN 597Brake switch · The truck's control module (ECU) reports a fault on: Brake switch.
- SPN 598Clutch switch · The truck's control module (ECU) reports a fault on: Clutch switch.
- SPN 789 FMI 7Trailer ABS · ABS is disabled: the brakes still work, the assist does not.
- SPN 1067ABS event · The truck's control module (ECU) reports a fault on: ABS event.
Chassis
Cooling
EGR
- P0401EGR flow insufficient · The truck's control module (ECU) reports a fault on: EGR flow insufficient.
- SPN 27EGR valve position · The truck's control module (ECU) reports a fault on: EGR valve position.
- SPN 411EGR differential pressure · The truck's control module (ECU) reports a fault on: EGR differential pressure.
- SPN 412EGR temperature · The truck's control module (ECU) reports a fault on: EGR temperature.
- SPN 2791EGR valve control · The truck's control module (ECU) reports a fault on: EGR valve control.
Electrical / J1939
- P0562System voltage low · The truck's control module (ECU) reports a fault on: System voltage low.
- SPN 168Battery / charging voltage · The truck's control module (ECU) reports a fault on: Battery / charging voltage.
- SPN 6205V sensor supply · The truck's control module (ECU) reports a fault on: 5V sensor supply.
- SPN 627ECU power supply · The truck's control module (ECU) reports a fault on: ECU power supply.
- SPN 639 FMI 2Data bus · The truck network is losing communication between modules.
- SPN 1231J1939-1 datalink · The truck's control module (ECU) reports a fault on: J1939-1 datalink.
- SPN 2003Transmission datalink · The truck's control module (ECU) reports a fault on: Transmission datalink.
Engine
- SPN 51Throttle position · The truck's control module (ECU) reports a fault on: Throttle position.
- SPN 91Accelerator pedal position · The truck's control module (ECU) reports a fault on: Accelerator pedal position.
- SPN 98Engine oil level · The truck's control module (ECU) reports a fault on: Engine oil level.
- SPN 190Engine speed · The truck's control module (ECU) reports a fault on: Engine speed.
- SPN 512Driver's demand torque · The truck's control module (ECU) reports a fault on: Driver's demand torque.
- SPN 1569 FMI 31Torque derate · The engine is deliberately limiting power.
Fuel
- P0088Rail pressure too high · The truck's control module (ECU) reports a fault on: Rail pressure too high.
- SPN 94Fuel delivery pressure · The truck's control module (ECU) reports a fault on: Fuel delivery pressure.
- SPN 97Water in fuel · The truck's control module (ECU) reports a fault on: Water in fuel.
- SPN 157Injector rail pressure · The truck's control module (ECU) reports a fault on: Injector rail pressure.
- SPN 651Injector cylinder 1 · The truck's control module (ECU) reports a fault on: Injector cylinder 1.
Lubrication
SCR / DEF
- P20EESCR efficiency below threshold · The truck's control module (ECU) reports a fault on: SCR efficiency below threshold.
- SPN 3055Aftertreatment intake NOx · The truck's control module (ECU) reports a fault on: Aftertreatment intake NOx.
- SPN 3216SCR intake NOx sensor · The truck's control module (ECU) reports a fault on: SCR intake NOx sensor.
- SPN 3226SCR outlet NOx sensor · The truck's control module (ECU) reports a fault on: SCR outlet NOx sensor.
- SPN 3361DEF dosing unit · The truck's control module (ECU) reports a fault on: DEF dosing unit.
- SPN 3364 FMI 18DEF quality · The system detected DEF that is out of specification.
- SPN 3516DEF concentration · The truck's control module (ECU) reports a fault on: DEF concentration.
- SPN 4094NOx limits exceeded — derate · The truck's control module (ECU) reports a fault on: NOx limits exceeded — derate.
- SPN 4364SCR conversion efficiency · The truck's control module (ECU) reports a fault on: SCR conversion efficiency.
- SPN 5246 FMI 0DEF inducement · The DEF system triggered the derate: road speed is about to be limited.
- SPN 5394DEF dosing valve · The truck's control module (ECU) reports a fault on: DEF dosing valve.
- SPN 5571DEF high pressure relief · The truck's control module (ECU) reports a fault on: DEF high pressure relief.
Transmission
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